This is yet another reason why removing chat is such a terrible idea in Feast.

Marked targets most often denote a priority targets to attack; HOWEVER, there could also be marked just to make it easier to keep tabs on them during the match. This is especially useful to healers, because it makes it easier for them to see when an enemy target is gunning for them. 8v8, in particular, can get kind of cluttered, so it helps clear up where everyone is. In 4v4, a marked target is almost always a priority target for a number of reasons (high stacks, high threat, healer shut down, no defensive buff, shut down offensive buff, etc). In 8v8, it could be a kill order, or it could just be a way of putting some order to the chaos. In an ideal world, the person marking could use chat to explain their thinking. If FFxiv, you just have to guess because chat is supposedly evil.